SET

Name

Synopsis

Description

The SET command changes run-time
configuration parameters. Many of the run-time parameters listed
in Chapter 18 can be changed
on-the-fly with SET. (But some require
superuser privileges to change, and others cannot be changed
after server or session start.) SET only
affects the value used by the current session.

If SET (or equivalently SET SESSION) is issued within a transaction that
is later aborted, the effects of the SET
command disappear when the transaction is rolled back. Once the
surrounding transaction is committed, the effects will persist
until the end of the session, unless overridden by another
SET.

The effects of SET LOCAL last only
till the end of the current transaction, whether committed or
not. A special case is SET followed by
SET LOCAL within a single transaction:
the SET LOCAL value will be seen until
the end of the transaction, but afterwards (if the transaction is
committed) the SET value will take
effect.

The effects of SET or SET LOCAL are also canceled by rolling back to a
savepoint that is earlier than the command.

If SET LOCAL is used within a
function that has a SET option for the
same variable (see CREATE FUNCTION), the effects of
the SET LOCAL command disappear at
function exit; that is, the value in effect when the function was
called is restored anyway. This allows SET
LOCAL to be used for dynamic or repeated changes of a
parameter within a function, while still having the convenience
of using the SET option to save and
restore the caller's value. However, a regular SET command overrides any surrounding function's
SET option; its effects will persist
unless rolled back.

Note: In PostgreSQL versions 8.0 through 8.2, the
effects of a SET LOCAL would be
canceled by releasing an earlier savepoint, or by successful
exit from a PL/pgSQL
exception block. This behavior has been changed because it
was deemed unintuitive.

Parameters

SESSION

Specifies that the command takes effect for the current
session. (This is the default if neither SESSION nor LOCAL
appears.)

LOCAL

Specifies that the command takes effect for only the
current transaction. After COMMIT
or ROLLBACK, the session-level
setting takes effect again. Note that SET LOCAL will appear to have no effect if
it is executed outside a BEGIN
block, since the transaction will end immediately.

configuration_parameter

Name of a settable run-time parameter. Available
parameters are documented in Chapter 18 and below.

value

New value of parameter. Values can be specified as
string constants, identifiers, numbers, or comma-separated
lists of these, as appropriate for the particular
parameter. DEFAULT can be written
to specify resetting the parameter to its default value
(that is, whatever value it would have had if no SET had been executed in the current
session).

Besides the configuration parameters documented in Chapter 18, there are a few that can
only be adjusted using the SET command
or that have a special syntax:

SCHEMA

SET SCHEMA 'value' is an alias for
SET search_path TO value. Only one schema can be
specified using this syntax.

NAMES

SET NAMES value is an alias for SET client_encoding TO value.

SEED

Sets the internal seed for the random number generator
(the function random).
Allowed values are floating-point numbers between -1 and 1,
which are then multiplied by 231-1.

The seed can also be set by invoking the function
setseed:

SELECT setseed(value);

TIME ZONE

SET TIME ZONE value is an alias for SET timezone TO value. The syntax SET TIME ZONE allows special syntax for the
time zone specification. Here are examples of valid
values:

'PST8PDT'

The time zone for Berkeley, California.

'Europe/Rome'

The time zone for Italy.

-7

The time zone 7 hours west from UTC (equivalent to
PDT). Positive values are east from UTC.

INTERVAL '-08:00' HOUR TO
MINUTE

The time zone 8 hours west from UTC (equivalent to
PST).

LOCALDEFAULT

Set the time zone to your local time zone (that
is, the server's default value of timezone; if this has not been
explicitly set anywhere, it will be the zone that the
server's operating system defaults to).

Notes

The function set_config provides
equivalent functionality; see Section 9.24. Also, it is possible to
UPDATE the pg_settings system view to perform the
equivalent of SET.

Examples

Set the schema search path:

SET search_path TO my_schema, public;

Set the style of date to traditional POSTGRES with "day
before month" input convention:

SET datestyle TO postgres, dmy;

Set the time zone for Berkeley, California:

SET TIME ZONE 'PST8PDT';

Set the time zone for Italy:

SET TIME ZONE 'Europe/Rome';

Compatibility

SET TIME ZONE extends syntax defined
in the SQL standard. The standard allows only numeric time zone
offsets while PostgreSQL allows
more flexible time-zone specifications. All other SET features are PostgreSQL extensions.

See Also

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